In three of the following four number pairs, the numbers are related in the same way and thus form a group. Which number pair DOES NOT belong to that group? 
(NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into their constituent digits. E.g. 13 – Operations on 13 such as adding / subtracting /multiplying to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.)

Logic: (1st number)³ = 2nd number

Now, we check each options.

Option (a): 4 : 64 (Follow)

(4)³ = 64​

Option (b): 8 : 512 (Follow)​

(8)³ = 512​

Option (c): 6 : 212 (Not Follow)​

(6)³ $$\neq$$ 212​

Option (d): 10 :1000 (Follow)​

(10)³ = 1000​

Thus, correct option is (c).